(1) Field of the Invention
This invention pertains to an improved method of operation and related structure of engine lathes. Engine lathe operators have ordinary skill in this art.
(2) Description of the Related Art
Lathes are a relatively old art. The design and operation of engine lathes has remained mostly unchanged from the early 1900's. The term engine lathe generally encompasses smaller less expensive lathes. Machine shops with lathes will generally have several engine lathes to do the bulk of their work and, if at all, they will typically have only one turret lathe. Because engine lathes are inexpensive, as compared to turret lathes, hourly operation costs are lower. In addition, engine lathes are less sophisticated than modern turret lathes and are therefore operated by junior personnel whose hourly rates are lower. Overall, having machine work done on an engine lathe is less expensive than having the same work done on a turret lathe.
An engine lathe, by virtue of its simplicity, cannot perform the functions of the more sophisticated turret lathes. More specifically, boring operations performed on an engine lathe before this invention were a time consuming and labor intensive operation. For example, on a typical job of drilling a 23/8" hole in a stainless steel shaft for a total length of about 23", the cutting time for drilling the hole will take about 50 minutes. This means that a machinist must hand advance the drill into the workpiece for 50 minutes being in constant attendance.
In the art before this invention, the tailstock is loosened so that it slides along the tracks of the lathe. The tailstock is moved toward the workpiece until the tool is in close proximity to the workpiece. The tailstock is locked in position. The workpiece is rotated by operation of a rotable chuck. The tool is advanced into the workpiece by cranking a hand wheel that advances a spindle out of the tail-stock toward the workpiece. Therefore, a machinist must be in constant attendance of the machine slowly rotating a hand wheel to advance the tool into the workpiece.
It is known in the art before this invention to advance the tailstock toward the workpiece automatically; however, the advancement is accomplished by attaching the tailstock to the lathe carriage. Advancement is then accomplished by the lathe carriage pulling the tailstock toward the workpiece. A lathe carriage is designed for precision movement, e.g. cutting threads. Lathe carriages are not designed to withstand the large force necessary to advance the tailstock against a hard workpiece, e.g. stainless steel. Even though advancement may be automatic by this method, a machinist's attention is still required since the lathe carriage cannot automatically stop at a predetermined position.